Eurocopter AS350 B3 accident near Reno, Nevada, January 17, 2010
On January 17, 2010 at about 8:50 pm local time, a Eurocopter AS350 B3 (helicopter), registered N904CF, was substantially damaged in an accident near Reno, Nevada (Washoe Medical Center Heliport airport). It was a positioning flight under general aviation rules (Part 91). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The improper installation of the engine-to-main gear box flex coupling, which resulted in the failure of the flex coupling and a loss of power to the rotor system during takeoff. Contributing to the accident was the mechanic who removed the engine's failure to follow the operator’s maintenance procedures. Also contributing was the Quality Assurance inspector's failure to follow the operator’s post-maintenance inspection requirements.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- January 17, 2010 · about 8:50 pm local time
- Place
- Reno, Nevada · Washoe Medical Center Heliport · map
- Type
- Accident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Eurocopter AS350 B3 · all AS350 B3s on the register
- Registration
- N904CF · registry record · serial 3676
- Damage
- Substantial damage
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot reported that he lifted the single-engine helicopter from the helicopter pad for the emergency medical service positioning flight to pick up a patient. The pilot maneuvered the helicopter into a 25-foot hover and, just as he was beginning the transition to forward flight, he heard a loud bang. The helicopter experienced a power loss and the pilot lowered the collective slightly, resulting in a hard landing on the pad. A surveillance camera that captured the accident sequence indicated that after the helicopter lifted into a hover over the pad, the nose abruptly rotated right 90 degrees and the helicopter descended vertically in a slight nose-down attitude, landing hard on the helipad. The postaccident airframe examination revealed that the nuts that attach the engine-to-main gear box flex coupling were not present on their respective bolts. The nuts and associated washers were located loose and clumped together just forward of the gimbal ring in the transmission input housing. An examination of the bolts and flex coupling by the Safety Board Materials Laboratory concluded that the nuts most likely had been hand tightened and that cotter pins had not been installed on the bolts. The improper installation lead to the failure of the flex coupling and resulted in a loss of power to the rotor system. Maintenance records showed that 59 flight hours before the accident the engine had been removed, the helicopter painted, and then the engine was reinstalled. The time between the engine removal and the reinstallation was 88 days. The mechanic who removed the engine stated that he removed the bolts to the engine-to-main gear box flex coupling, and then partially reassembled the flex coupling bolts. This action was not in accordance with the AS350 maintenance manual engine removal procedure. The mechanic who installed the engine 88 days later stated that he did not check the flex coupling bolts because the removal of those bolts is not specified in the maintenance manual as part of the engine removal or replacement procedure. The overall maintenance activity involved a 100-hour inspection, which included a visual inspection of the engine-to-main gear box flex coupling. Although a visual inspection of the engine-to-main gear box flex coupling is a required action, the Quality Assurance inspector signed off the maintenance without performing the visual inspection of the flex coupling.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Autorotation Collision with terrain or object (not controlled flight into terrain) defining event
- Loss of engine power (total) during takeoff
The NTSB's findings
- cause Personnel issues › Task performance › Maintenance › Installation › Maintenance personnel
- factor Aircraft › Aircraft propeller/rotor › Main rotor drive › Engine/transmission coupling › Not inspected
- factor Aircraft › Aircraft propeller/rotor › Main rotor drive › Engine/transmission coupling › Incorrect service/maintenance
- cause Aircraft › Aircraft propeller/rotor › Main rotor drive › Engine/transmission coupling › Failure
Pilot
- Certificate: commercial pilot
- Ratings: instructor: helicopter; instrument: helicopter; rotorcraft: helicopter
- Flight time: 14,300 hours in all; 9,544 in this make and model; 46 in the last 90 days; 11 in the last 30 days; 13,700 as pilot in command
- Last flight review: November 5, 2009
- Medical certificate: Class 1 (with waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 3,940 hours
- Last inspection: approved inspection programme, January 17, 2010; 0 hours since
- Seats: 4
- Landing gear: fixed
- Engine: Turbomeca Arriel 2B1 (turboshaft); 0 hours total
- Operator: Air Methods
The flight
- Departed from: NV57 Reno NV at 8:50 pm
- Destination: Winnemucca NV
Weather at the time
- Light: daylight
- Wind: from 170° at 13 knots, gusting 18
- Visibility: 10 statute miles
- Sky: broken clouds at 9,000 ft; scat at 6,000 ft
- Temperature: 52°F (11°C), dew point 30°F (-1°C)
- Altimeter: 29.71 inHg
- Observation at 8:55 pm from KRNO, 2 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 3 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.